Lower Lumbar Spine Disc Degeneration L4-L5

Lower lumbar spine of an old man with pronounced disc degenerations L4–L5 and L5–S1. The intact torso had been frozen in axial rotation. At L4–L5 the root traversing the lateral recess is severely compressed. Anteriorly there is a motion–induced (functional) retrolisthesis of L4 on L5 that also causes the grossly disrupted disc to move posteriorly. Posteriorly the lateral portion of the lamina and the most medial portion of the superior articular process of L5 (5) have moved anteriorly due to the rotation and squeeze the L5 root against the disc. Note the gaping (vacuum phenomenon) in the joint. At L5–S I degenerated disc material pushes the outermost annulus posteriorly and also has caused detachment of (thickened) periosteum from the vertebral body (contained disc herniation). At the lower insertion of the annulus a marked sclerotic spondylophyte projects posteriorly, compressing the SI root against the infolding ligamentum flavum.